Bipolar electrolyser



0. DE NORA 2,346,384

BIPOLAR ELECTROLYSER I 2 Sheets-Sheet 1 INVENTOR.

I l l l l l l l o i i 1 b i I i i OI'OIZZZIO a e A Zrn Aug. 5, 1958 Filed June 30, 1954 Aug. 5,1958 0. DE NORA BIPOLAR ELECTROLYSER 2 Sheets-Sheet 2 Filed June 30, 1954 III/III IIIIJI/IIIIIIIIIIIIIIIIIIIIIII FIG. 2

.J. n IIL H INVENTOR. ronzw jv'ora BIPOLAR ELECTRQLYSER Oronzio De Nora, Milan, Italy, assignor to Oronzio De Nora lmpianti Elettroehimici, Milan, Italy, a corporation of Italy Application June 30, 1954, Serial No. 440,425

Claims priority, application Italy December 5, 1953 9 Claims. (Cl. 204-129) The invention relates to bipolar electrolysers, especially those for producing gases from liquids, such as oxygen and hydrogen from water.

Conventional electrolysers of this kind generally consist of a battery of electrolysis cells and theirframes, which are packed together in the manner of a filter-press Between each cell and the next in the assembly there is a metal panel, which serves as a partition between the adjacent cells and as an eletrode for both of the cells, and which also holds an auxiliary electrode spaced from each of its opposite faces in the respective adjacent cells. The auxiliary electrodes are composed of perforated plates, or the like, suitable for promoting the evolution of gas from the liquid being electrolyzed. The gas evolves mainly in the intermediate spaces between the auxiliary electrodes and the primary electrode panels which hold them. Each cell is bounded by two main electrode panels and is divided into an anodic compartment and a cathodic compartment by a diaphragm extending between the auxiliary electrodes in the cell attached to its respective main electrode panels. Such diaphragm opposes cross-diffusion of the oxygen and hydrogen produced by the respective electrodes, so that oxygen can be drawn off from the anodic compartment, while hydrogen is drawn ofi from the cathodic compartment.

While the conventional single-diaphragm separation system is effective to some extent, it represents only a partial solution of the problem. The diaphragm must have sufficient permeability to the electrolyte to pass current without an excessively high voltage drop, and such premeability is accompanied by some permeability to the gases with resultant cross-diffusion of the gases, even when an eifort is made to equalize the discharge pressures of the two separate streams of gases. Moreover, there is always the possibility of one gas outlet becoming obstructed, which increases the diffusion of the gas in one of the compartments into the other compartment of the cell. That not only decreases the purity of at least one of the gases but also may form a dangerously explosive mixture of gases.

In accordance with the present invention such difiiculties are obviated by use of a plurality of diaphragms forming one or more intermediate compartments venting to the atmosphere. The invention further provide an efiective automatic system of balancing the back-pressures on the cell compartments of opposite polarity, notwithstanding large dilferences in the rates of volumetric evolution of the different gases generated in the cells.

Other advantages, objects and features of the invention will become apparent from the following detailed description of a present preferred embodiment of the in vention, which is shown, for purposes of illustration only, in the accompanying drawing. In the drawing:

Figure 1 shows a semi-diagrammatic side elevation of electrolysis apparatus embodying the invention; and

Figure 2 is a section on the line 11-11 in Figure 1, partially broken away to show the interior of one of the electrolysis cells.

2,846,384 PatentedAug. 5, 1958 Referring now more particularly to the drawing, there is shown a battery 10 of electrolysis cells 11, one of which is designated 11a and shown in cross-section in Figure 2 in order to reveal its internal structure. A pair of spaced parallel metal panels 12 and 13 separate the cell 1111 from the adjacent cells. The panel 12 is charged as an anode, and through studs 16 isconnected on one side to a parallel auxiliary anode 14in compartment 26 of cell 11a, and similarly on its opposite side where it is charged as a cathode, it is connected to a like auxiliary cathode in an adjacent cell 11. The panel 13 is charged as a cathode, and through studs'16 is connected on one side to a parallel auxiliary cathode 15 in compartment 21 of cell 11a, and similarlyon itsopposite side to a like auxiliary anode in the other adjacent cell 11. A pair of parallel spaced diaphragms 17 and 18 extend between the auxiliary electrodes 14 and 15, and a frame 19 extends around and supports the'peripheral edges of panels 12 and 13 and diaphragms 17 and 13. The frame 19 is electrically insulated and is sealed around said edges to form a compartment. .betweenvpanel 12 and diaphragm 17, a compartment 21 between panel 13 and diaphragm 13, and an intermediate compartment 22 between the diaphragms 17 and 18. Thesev compartments are tilled with the liquid to be electrolyzed, and the gas evolved around the auxiliary anode 14 passes out of compartment. 21) through an upper outlet pipe 23, while the gas evolved around auxiliary cathode 15 passes out of the compartment 21 through an upper outlet pipe 24. When water is to be electrolyzed, for example, the compartments 2022 are filled with water through suitable connections (not shown). The diaphragms 17 and 13 are of conventionalmaterial suitable for the purpose, which is largely impermeable to the oxygen evolved by the anodes 12 .and 14 in. compartment 20 and tothe hydrogen evolved by the cathodes 13 and 15 in compartment 21, but is sufficiently permeable to the water and the electrolytic additive dissolved therein to allow current to pass between the anode 14 and cathode .15 without excessive voltage'drop. Whatever .quantitives of oxygen and hydrogen do pass through the diagrams 17 and 18, respectively, mm the compartments 2t) and 21, are not transferred between the compartments Zttl and 21, but instead are received in compartment 22 and vented therefrom through an upper. outlet pipe 25. This preserves the purity of the gases generated in the compartments 2t) and 21, and prevents the accumulation of dangerous explosive mixtures of oxygen and hydrogen.

The oxygen generated in compartment 20 passes out through pipe 23 into a separator tank 26, and from there passes through a pipe 27 and discharges .through a submerged nozzle 28 into a bubbler compartment 2% in a tank 31:. A pipe 31 draws off the oxygen gas collecting in the bubbler compartment 29,v and delivers it Where required for further processing or use. Some of the electrolytic bath in the compartment 20 is carried up with the oxygen passing through pipe 23 into the separator tank 26, and it is drained from the tank 26 through a pipe 32 back to the compartment 20 (and to the corresponding anodic compartments of the other cells 11, the connections being omitted in the drawing for purposes of simplicity). The return'pipe32 passes through a cooler 33 having inlet and outlet pipes 34 and 35 for circulation of cooling fluid to cool the fluid returning through pipe 32.

The cathodic compartment 21 similarly vents hydrogen gas through pipe 24 into a separator tank 36, which returns electrolyte through a pipe 37 and cooler 38 to the compartmentlrl (and to the. corresponding cathodic compartments of the cells 11, through connections omitted in the drawing for the purposes of simplicity), while the hydrogen in tank 36 passes through a'pipe 359' and submerged nozzle 40 into a bubbler compartment 41 in tank 30, and thence through a pipe 42 for further processing or use.

The separator tanks 26 and 36 are connected to the respective anodic and cathodic compartments of each of the cells 11 through suitable connections corresponding to the pipes 23 and 24 (said connections being omitted in the drawing for purposes of simplicity), so that the outlet pipes 27, 32, 39, and 37 receive the combined output of oxygen, electrolyte carried over with the oxygen, hydrogen, and the electrolyte carried over with the hydrogen, respectively, from the whole battery of cells 11, and the pipes 32 and 37, as previously stated, return the electrolyte from tanks 26 and 36 to the respective anodic and cathodic compartmenes of the whole battery of cells 11. The tanks 26 and 36 preferably extend transversely across the length of the whole battery of cells, but are shown of less length in the drawings for purposes of diagrammatic illustration.

An auxiliary tank 43 receives overflow from a standpipe or riser 44 projecting up into the interior of tank 30, and receives gases discharged from between the diaphragms 17 and 18 through pipe-25. An opening 45 vents the interior of tank 43 to the atmosphere, and a pipe 46 drains liquids collecting in the tanks 43 and re turns it (by connections not illustrated) to the cells 11. A by-pass pipe 47 connects the pipe 44 directly to the pipe 46, and valves 48 and 49 control the division of' flow from pipe 44 to tank 43 and to the by-pass pipe 47.

The tank 30 not only cools and washes the gases received from pipes 27 and 39, but also maintains substantially equal static back-pressure in the compartments 2t) and 21 and outlet pipes 23 and 24. Partitions 50, 51 and 52 extend across the interior tank 30 from its top to a level close to but spaced from its bottom, and subdivide the tank into the aforesaid bubbler compartments 29 and 41 at opposite ends of the tank, and into two intermediate compartments 53 and 54. The standpipe 44 is located in compartment 53 and limits the maximum liquid level in that compartment and also in compartment 54, since compartments 53 and 54 are vented to the atmosphere through openings 55 and 56. The tank 30 is filled with water to the point of overflow through standpipe 44, and some of this Water is received in the bubbler compartments 29 and 41 to submerge the nozzles 28 and 40. The water level in the bubbler compartments 29 and 41 is variable, depending on the amount of back-pressure on the respective gases at the outlet pipes 31 and 42. However, whatever the back pressure and water level may be in the respective bubbler compartments 29 and 41, the back pressure on the open mouths of the nozzles 28 and 40 is always equal to the head of water at a depth equal to the length of the standpipe 44 from its open top down to the level of the mouths of the nozzles 28 and 40, plus atmospheric pressure. Consequently, since the mouths of the nozzles 28 and 40 are placed at the same level, the static back pressure through pipes 27, 23 and 32 to the anodic compartment 20, and through pipes 39, 24 and 37 to the cathodic compartment 21, remains equal under normal conditions. If a surge of gas passes out of either of the nozzles 28 and 40 the resultant pressure in the adjacent bubbler compartments 29 and 41 as the case may be is relieved not only through the normal outlet pipe 31 or 42 connected to the bubbler compartment receiving the surge of gas, but is also relieved'through one of the intermediate compartments 53 or 54, which can relieve the excess pressure by overflow through pipe 44 into tank 43, or by venting the surge of gas to the atmosphere through one of the openings 55 and 56.

While a present preferred embodiment of the invention has been illustrated and described, it will be recognized that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

I claim:

1. Apparatus for producing different gases by electrolysis of a liquid, comprising an anode and cathode, a compartment for containing a body of liquid electrolyte in contact with the anode and for collecting gas produced from the electrolyte by the anode, a compartment for containing a body of liquid electrolyte in contact with the cathode and for collecting gas produced from the electrolyte by the cathode, at least a pair of spaced diaphragms permeable to liquid electrolyte, an intermediate compartment separated from the other said compartments by said diaphragms, means venting the upper end of the interior space in the intermediate compartment to the atmosphere, a tank for holding a body of liquid, partitions dividing the tank into a series of compartment with open passageways adjacent the bottom of the tank for free flow of said body of fluid between said tank compartments, means venting at least one of said tank compartments to the atmosphere, means venting gas in the anode compartment into another of the tank compartments at a level below the upper surface of the said body of liquid, means venting gas in the cathode compartment into still another of the tank compartments at the same said level, and separate means for Withdrawing gas bubbled through the liquid in-each of the said other tank compartments.

2. Apparatus according to claim 1 including an overflow discharge pipe having an .open receiving end in said tank at a level above the said level of discharge of the anode and cathode gases into the body of liquid in the tank.

3. Apparatus according to claim 1 in which at least two of the atmosphere-vented tank compartments are interposed between the tank compartments receiving the anode and cathode gases, respectively.

4. Apparatus according to claim 1 in which the means for venting gas from each electrode compartment to the said tank comprises an auxiliary tank, a conduit receiving gas in the electrode compartment and discharging it into an upper level of the auxiliary tank, a conduit receiving gas in the auxiliary tank and'discharging into the tank containing the body of fluid, a conduit connected to receive liquid collected in the bottom of the auxiliary tank and to return it to the electrode compartment, and means for cooling fluid in the latter conduit.

5. Apparatus for producing different gases by electrolysis of a liquid, comprising an anode and cathode, a compartment for containing a body of liquid electrolyte in contact with the anode and for collecting gas produced from the electrolyte by the anode, a compartment for containing a body of liquid electrolyte in contact with the cathode and for collecting gas produced from the electrolyte by the cathode, an intermediate compartment between said anode and cathode compartments, diaphragm means permeable to liquid electrolyte interposed between said anode, intermediate and cathode cornpartments, means for venting gases from said intermediate compartment to the atmosphere, a tank for holding a body of liquid, partitions dividing the tank into a series of com partments with open passageways adjacent the bottom of the tank for free flow of said body of fluid between said tank compartments, an overflow discharge pipe having an open receiving end in the tank above the level of said passageways, means for venting gases from the compartment containing said discharge pipe, means venting gas in the anode compartment into another of the tank compartments at a level below the level of the said receiving end of the discharge pipe, means venting gas in the cathode compartment into still another of the tank compartments at the same level at which the anode gas is vented into the liquid in the tank, and separate means for withdrawing gas bubbled through the liquid in each of the said other tank compartments.

6. A method of producing gases by electrolysis, comprising the steps of feeding electrolyte into an anode chamber and into a separate cathode chamber, passing electric current between an anode in the anode chamber and a cathode in the cathode chamber through the electrolyte in said chambers, and collecting the gases from said anode and cathode chambers, the improvement which comprises, passing said electric current through a diaphragm bounding one side of one of said chambers and a second diaphragm spaced from the first and bounding one side of the other of said chambers, and also through a body of electrolye in the space between said diaphragms, venting the top of said body of electrolyte to the atmosphere, maintaining a static back pressure on said body of electrolyte and separately drawing ofi the gases evolved by electrolysis in the anode and cathode cells, respectively, while maintaining equal pressures on the anode face of the diaphragm adjacent the anode chamber and the cathode face of the diaphragm adjacent the cathode chamber by maintaining an equal back pressure on the said gases in excess of atmospheric and at least equal to the pressure on the diaphragm faces in said intermediate chamben 7. The method of claim 6, in which the steps are carried on simultaneously and continuously.

8. In a process for producing gases by electrolysis wherein an electrolyte is passed into separate anode and cathode chambers separated by a diaphragm, and the gases evolved at the anode and cathode are withdrawn from the anode and cathode chambers respectively, the improvement which comprises, preventing diffusion and intermixing of gases between the anode and cathode compartments by the steps comprising, interposing a chamber for electrolyte fluid between the anode and cathode chambers, providing diaphragms to separate the intermediate chamber from the anode and cathode chambers respectively, maintaining equal back pressure on the anode and cathode sides of the diaphragms adjacent the anode and cathode respectively by maintaining equal back pressures on the gases withdrawn from the anode and cathode chambers respectively, said pressure 6 being greater than atmospheric pressure and at least equal to the pressure on the diaphragm faces in said intermediate chamber, and venting any gases which pass through said diaphragms from said anode and cathode chambers by collecting said gases in said intermediate chamber and venting said gases therefrom.

9. In a process for continuously producing hydrogen and oxygen gases from water by electrolysis, comprising the simultaneous and continuous steps of feeding said water into separate anode and cathode compartments, passing an electric current between said compartments, and separately drawing off the oxygen and hydrogen gases evolved by electrolysis in the anode and cathode compartments, the improvement which comprises, preventing ditfusion and intermixing of gases between the anode and cathode compartments by the steps comprising, interposing a chamber for electrolyte fluid between the anode and cathode chambers, providing diaphragms to separate the intermediate chamber from the anode and cathode chambers respectively, maintaining equal back pressure on the anode and cathode sides of the diaphragms adjacent the anode and cathode respectively by maintaining equal back pressure on the gases withdrawn from the anode and cathode chambers respectively, said pressure being greater than atmospheric pressure and at least equal to the pressure on the diaphragm faces in said intermediate chamber, and venting any gases which pass through said diaphragms from said anode and cathode chambers by collecting said gases in said intermediate chamber and venting said gases therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 518,786 Le Sueur Apr. 24, 1894 571,591 Hargreaves Nov. 17, 1896 2,636,852 Juda et al. Apr. 28, 1953 FOREIGN PATENTS 677,573 France Dec. 18, 1929 864,256 France Jan. 13, 1941 

1. APPARATUS FOR PRODUCING DIFFERENT GASES BY ELECTROLYSIS OF A LIQUID, COMPRISING AN ANODE AND CATHODE, A COMPARTMENT FOR CONTAINING A BODY OF LIQUID ELECTROLYTE IN CONTACT WITH THE ANODE AND FOR COLLECTING GAS PRODUCED FROM THE ELECTROLYTE BY THE ANODE, A COMPARTMENT FOR CONTAINING A BODY OF LIQUID ELECTROLYTE IN CONTACT WITH THE CATHODE AND FOR COLLECTING GAS PRODUCED FROM THE ELECTROLYTE BY THE CATHODE, AT LEAST A PAIR OF SPACED DIAPHRAGMS PERMEABLE TO LIQUID ELECTROLYTE, AN INTERMEDIATE COMPARTMENT SEPARATED FROM THE OTHER SAID COMPARTMENTS BY SAID DIAPHRAGMS, MEANS VENTING THE UPPER END OF THE INTERIOR SPACE IN THE INTERMEDIATE COMPARTMENT TO THE ATMOSPHERE, A TANK FOR HOLDING A BODY OF LIQUID, PARTITIONS DIVIDING THE TANK INTO A SERIES OF COMPARTMENT WITH OPEN PASSAGEWAYS ADJACENT THE BOTTOM OF THE TANK FOR FREE FLOW OF SAID BODY OF FLUID BETWEEN SAID TANK COMPARTMENTS, MEANS VENTING AT LEAST ONE OF SAID TANK COMPARTMENTS TO THE ATMOSPHERE, MEANS VENTING GAS IN THE ANODE COMPARTMENT INTO ANOTHER OF THE TANK COMPARTMENTS AT A LEVEL BELOW THE UPPER SURFACE OF THE SAID BODY OF LIQUID, MEANS VENTING GAS IN THE CATHODE COMPARTMENT INTO STILL ANOTHER OF THE TANK COMPARTMENTS AT THE SAME SAID LEVEL, AND SEPARATE MEANS FOR WITHDRAWING GAS BUBBLED THROUGH THE LIQUID IN EACH OF THE SAID OTHER TANK COMPARTMENTS. 